diff --git a/subprojects/libvduse/libvduse.c b/subprojects/libvduse/libvduse.c
index e089d4d546..c871bd331a 100644
--- a/subprojects/libvduse/libvduse.c
+++ b/subprojects/libvduse/libvduse.c
@@ -16,6 +16,10 @@
  * later.  See the COPYING file in the top-level directory.
  */
 
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdbool.h>